Warframe was one of several free-to-play games available on PlayStation 4 for the console's launch. When we reviewed it all the way back in December of 2013 (that long ago? Really?) it's safe to say that we were critical. Back then, the third-person action title was still technically in its beta phase on Sony's system, and it had more than a few rough edges. Skip forward four whole years or so, and we've decided to take another look at Digital Extreme's popular ongoing project.

Truth be told, we never had much interest in returning to Warframe once our review was done. We wrote the odd news story about big updates here and there, but there was no desire to actually jump back in and play it. That changed recently when we heard about a certain "open world" update that's in the works. Titled Plains of Eidolon, the huge update is due later this year, and adds a totally open environment to the game -- the first of its kind.

Now, we're not open world addicts or anything, but the news that a four-year-old title was being built upon so significantly certainly piqued our interest. We've been told numerous times over the years that the game has seen drastic improvements, and in short, we finally felt the need to hit up the PlayStation Store and get that 19GB file downloading.

And boy are we glad that we did, because Warframe has evolved into something quite special. For a free-to-play title, its scope is now seriously impressive. Hundreds of missions are yours to undertake either alone or with other players, and the various role-playing and loot mechanics offer up some real depth. The experience is packed to bursting point with content and potential.

So what's changed since we last played four years ago? Well, there's a snappy tutorial mission now, which does an admirable job of explaining general gameplay. Following on from that, a series of story missions take you through the equipment and crafting elements of the release, setting you up nicely for the inevitable grind. After spending just half an hour with these introductory missions, we felt as though we understood the workings of Warframe better than we ever did over our entire 20 or so hour review run. If that's not a game-changing improvement, then we don't know what is.

As you can imagine, actually having a firm grasp of the basics is a big plus, and since then we've spent hours upon hours happily grinding away. Indeed, the grind is the core of Warframe. The title falls firmly into the same loot-driven camp as Diablo III as you blast through mission after mission, collecting resources and levelling up your abilities so that you can craft better and better equipment.

Grind-heavy games obviously aren't for everyone, but those who find satisfaction in the constant improvement of an in-game avatar will find Warframe an addictive experience. There are so many upgrades, mods, and blueprints to discover that there's always a new goal on the horizon -- a cool new weapon or frame (read: new playable character) to try out and maybe fall in love with.

Of course, none of this would actually matter if Warframe came up short in the gameplay department, but Digital Extremes has crafted a shockingly slick action title. Fast and deadly, combat is a hurricane of melee blows, third-person shooting, and super smooth movement. Sliding across the ground on your knees, running up walls, and spin-dashing through the air -- get a grip on the controls and it's brilliantly empowering stuff.

And no, you don't have to spend a penny to enjoy any of this. Warframe makes much of its money by offering instant access to frames, equipment, and cosmetic items. Exchange real money for in-game premium currency, and then use that to purchase the bits and pieces that you want. It's obviously an economy that works, but does this mean that the free experience is designed to be a slog?

Well, kind of, but that's the nature of the free-to-play model. Fortunately, we think Warframe's managed to find a good enough balance. Having to acquire blueprints and then manufacture gear certainly takes time, but it's by no means an impossible process. As long as you find yourself enjoying the grind and the action packed gameplay, then there's no real issue. Again, the generous amount of content that's available to you regardless of how much money you spend makes it hard to bear a grudge.

There's now so much more to Warframe than there was four years ago. It's matured into an addictive looter that's bolstered by slick gameplay and a suite of deep RPG systems. At its core it's still a free-to-play title, but if you're looking for a new PS4 addiction that doesn't have to cost you a penny, you simply can't go wrong.

Do you play Warframe on PS4? How long have you been playing? What do you think of it? Grab your weaponry and slide into the comments section below.

Robert's been a dedicated PlayStation fan since the days of Tekken 2, and he still loves a good dust up. When he's not practising combos, he's usually getting lost in the latest 100-hour RPG, or, y'know, replaying The Witcher 3.